1. Field of the Invention
The invention relates to an X-ray apparatus, comprising an X-ray source for generating an X-ray beam for irradiating an object to be examined, detection means for detecting X-rays having passed through the object, and a collimator which is arranged between the X-ray source and the object in order to collimate the X-ray beam so as to obtain a fan-shaped beam of adjustable thickness.
2. Description of the Prior Art
An X-ray apparatus of this kind is known from U.S. Pat. No. 4,419,764.
In the known X-ray apparatus, being an apparatus for making panoramic images, an object to be examined, for example a patient, is irradiated by a fan-shaped X-ray beam. Opposite the X-ray source there are arranged detection means for detecting the X-ray beam after passage through the patient. The detection means are shown as an X-ray sensitive film. The thickness of an irradiated slice of the patient is determined by the degree of collimation of the X-ray beam in a direction perpendicular to a plane of examination. For collimation a collimator in the form of a trunnion which is made of X-ray absorbing material is arranged near the X-ray source, said trunnion comprising a slit which extends in the axial direction. The X-ray beam emerging from the X-ray source is collimated to an adjustable thickness by rotating the trunnion around its longitudinal axis. A construction of this kind has the drawback that the edges of the collimator are easily damaged, giving rise to a beam of non-uniform thickness, and that the collimation at both sides of an X-ray beam occurs at different distances from the source, thus causing asymmetry in the X-ray beam.